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Background and Rationale

Streptococcus pneumoniae are bacteria that are frequently found in the upper respiratory tract of healthy children and adults. These bacteria, however, can also cause a range of infections—from relatively mild ear infections to fatal pneumonia, meningitis, and sepsis (bacterial blood infection).

Serious pneumococcal infections are a major global health problem. The World Health Organization (WHO) estimates that more than 1.6 million people—including more than 800,000 children under 5 years old—die every year from pneumococcal infections. Nearly all of these deaths occur in the world’s poorest countries.

Pneumococcal meningitis is the most severe form of pneumococcal disease and one of the most fatal childhood illnesses. In developing countries, it kills or disables 40 to 70 percent of children who get it.

Many of the children suffering from pneumococcal disease live in rural areas with high infant mortality rates, significant rates of malaria transmission, and very limited access to health care. In many ways, The Gambia is typical of such regions.

Overview of the Clinical Trial

To respond to the threat of pneumococcal infections in children, The Gambian government and the British Medical Research Council (MRC) conducted a study to determine whether a vaccine, which in previous studies had been found effective against pneumococcal disease in urban areas, also would work in the more challenging environment of rural Africa.

Over a 4-year period, a team of researchers vaccinated and followed more than 17,000 young children. The conjugate vaccine contained nine of the pneumococcal serotypes (subtypes) that are most common in The Gambia.

Results

Researchers found that the vaccine was 77 percent effective in preventing pneumococcal infections caused by the vaccine serotypes. As a result, there were 37 percent fewer cases of pneumonia in the children who received the vaccine compared with children who received the control vaccine.

Overall, the vaccine reduced childhood mortality by 16 percent in children who received it.

In addition, the vaccine significantly reduced the need for hospitalization. Vaccinated children had 15 percent fewer hospital admissions than those who did not.

Significance

The Gambia Pneumococcal Vaccine Trial was the first major randomized, controlled vaccine clinical trial in nearly 20 years to show a statistically significant reduction in overall child mortality.

Findings indicate that vaccinating infants against Streptococcus pneumoniae could substantially reduce death and illness among children in developing countries, including in rural areas with limited access to public health systems. If used widely, a pneumococcal conjugate vaccine could prevent hundreds of thousands of child deaths each year.

Trial Partners

The study was supported by a broad coalition of international partners, including NIAID, MRC, the London School of Hygiene and Tropical Medicine, WHO, the U.S. Agency for International Development, the Centers for Disease Control and Prevention, Wyeth-Lederle Vaccines, and the Program for Appropriate Technology in Health Children’s Vaccine Program.